Polishing apparatus

ABSTRACT

A polishing apparatus is used for polishing and planarizing a surface of a substrate such as a semiconductor wafer. The polishing apparatus includes a polishing table having a polishing surface, and a top ring configured to hold a substrate and press the substrate against the polishing surface. The top ring has an extendable and contractable connection sheet configured to cover a gap between a retainer ring guide fixed to a top ring body and a retainer ring guided by the retainer ring guide to move vertically. The polishing apparatus has a nozzle configured to eject a cleaning liquid in a horizontal direction toward the connection sheet and apply a flow of the cleaning liquid directly onto the connection sheet for cleaning the connection sheet.

CROSS REFERENCE TO RELATED APPLICATIONS

This document claims priorities to Japanese Application Number 2012-205394, filed Sep. 19, 2012, Japanese Application Number 2013-178935 filed Aug. 30, 2013, and Japanese Application Number 2013-185884 filed Sep. 9, 2013, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing apparatus, and more particularly to a polishing apparatus for polishing and planarizing a surface of an object to be polished (substrate) such as a semiconductor wafer.

2. Description of the Related Art

A polishing apparatus for polishing a surface of a semiconductor wafer generally includes a polishing table having a polishing surface formed by a polishing pad, and a top ring (polishing head) for holding the semiconductor wafer. The semiconductor wafer is held and pressed against the polishing surface of the polishing pad under a predetermined pressure by the top ring, and the polishing table and the top ring are moved relative to each other. Thus, the semiconductor wafer is brought into sliding contact with the polishing surface, so that the surface of the semiconductor wafer is polished to a flat mirror finish. In chemical mechanical polishing (CMP), a polishing liquid (slurry) is supplied onto the polishing surface during polishing.

In such polishing apparatus, if the relative pressing force applied between the semiconductor wafer, being polished, and the polishing surface of the polishing pad is not uniform over the entire surface of the semiconductor wafer, then the surface of the semiconductor wafer is polished insufficiently or excessively in different regions thereof, which depends on the pressing force applied thereto. It has been customary to uniformize the pressing force applied to the semiconductor wafer by providing a pressure chamber formed by an elastic membrane at a lower portion of the top ring and supplying the pressure chamber with a fluid such as air to press the semiconductor wafer under a fluid pressure through the elastic membrane.

In this case, the polishing pad is so elastic that pressing forces applied to a peripheral portion of the semiconductor wafer, being polished, become non-uniform, and hence only the peripheral portion of the semiconductor wafer may excessively be polished, which is referred to as “edge rounding”. In order to prevent such edge rounding from occurring and prevent the semiconductor wafer from slipping out of the top ring, a retainer ring for holding the peripheral edge of the semiconductor wafer is provided so as to be vertically movable with respect to the top ring body, thereby pressing an annular portion of the polishing surface of the polishing pad that corresponds to the peripheral portion of the semiconductor wafer.

In this manner, when the retainer ring for holding the peripheral edge of the semiconductor wafer is provided so as to be vertically movable with respect to the top ring body, a gap is formed between the top ring body and the retainer ring. Thus, during polishing, this gap allows a polishing liquid or the like supplied onto the polishing surface to enter therethrough into an interior of the top ring. Then, contaminants such as a polishing liquid are attached to the top ring, and the contaminants such as a polishing liquid are dried and fall onto the polishing pad, causing scratches on the substrate.

Therefore, the applicant of the present invention has proposed a polishing apparatus in which a gap formed between a retainer ring guide fixed to the top ring body and a retainer ring guided by the retainer ring guide to move vertically is covered with an extendable and contractable connection sheet, and a gap formed between the top ring body and an inner circumferential surface of the retainer ring is covered with a seal member, as disclosed in Japanese laid-open patent publication No. 2009-131946.

Further, there has been proposed a polishing apparatus having a nozzle for cleaning contaminants remaining on a membrane (elastic membrane) mounted on a bottom surface of a polishing head (top ring), and a nozzle for cleaning contaminants which have flowed into a space formed between an outer circumferential surface of the membrane and an inner circumferential surface of a retainer ring disposed at a lower peripheral portion of the polishing head, as disclosed in Japanese laid-open patent publication No. 2001-15466.

As described above, contaminants such as a polishing liquid are attached to the extendable and contractable connection sheet configured to cover a gap formed between the retainer ring guide fixed to the top ring body and the retainer ring guided by the retainer ring guide to move vertically, and the attached contaminants are dried and fall onto the polishing pad, causing scratches on the substrate. Therefore, it is necessary to clean the connection sheet.

Thus, the inventors of the present invention have conducted various experiments and obtained the following knowledge. Specifically, when the connection sheet is scrub-cleaned by a brush or the like, the initial effect does not last due to a loss of elasticity in the brush, re-contamination, and the like. If a cleaning nozzle is provided instead of the brush to clean the connection sheet by spraying a cleaning water onto the connection sheet, because the connection sheet is configured in a shape of bellows, the cleaning water does not reach inner portions of folded and overlapped portions of the bellows-like connection sheet to which the contaminants such as a polishing liquid are liable to be attached. Thus, the contaminants such as a polishing liquid remain in deep concave portions of the bellows-like connection sheet.

Further, this holds true for the seal member which covers the gap formed between the top ring body and the inner circumferential surface of the retainer ring. Specifically, when the cleaning water is sprayed onto the seal member from a cleaning nozzle to clean the seal member, because the seal member is configured in a deep concave shape so as to reach a deep inner portion of the gap, the cleaning water does not reach an inner part of the deep-concave-shaped seal member. Therefore, it is difficult to clean the entire surface of the seal member efficiently by the cleaning water.

SUMMARY OF THE INVENTION

Based on the above knowledge obtained from various experiments, the present invention has been made. It is therefore an object of the present invention to provide a polishing apparatus which can efficiently clean, by cleaning water, an extendable and contractable connection sheet for covering a gap formed between a retainer ring guide fixed to a top ring body and a retainer ring guided by the retainer ring guide to move vertically, and a seal member for covering a gap formed between the top ring body and the retainer ring, and also can prevent scratches caused by contaminants such as a polishing liquid attached to the top ring from occurring.

In order to achieve the above object, according to one aspect of the present invention, there is provided a polishing apparatus for polishing a substrate, comprising: a polishing table having a polishing surface; a top ring configured to hold a substrate and press the substrate against the polishing surface, the top ring having an extendable and contractable connection sheet configured to cover a gap between a retainer ring guide fixed to a top ring body and a retainer ring guided by the retainer ring guide to move vertically; and a nozzle configured to eject a cleaning liquid in a horizontal direction toward the connection sheet and apply a flow of the cleaning liquid directly onto the connection sheet for cleaning the connection sheet.

According to the present invention, by ejecting the cleaning liquid in a horizontal direction toward the connection sheet, configured to cover the gap between the retainer ring guide and the retainer ring, to apply the flow of the cleaning liquid directly onto the connection sheet, the connection sheet can be cleaned by the cleaning liquid efficiently even if the connection sheet is configured in a shape of bellows. Further, the connection sheet is kept wet by the cleaning liquid if needed, to prevent the contaminants such as a polishing liquid attached to the connection sheet from being dried.

In a preferred aspect of the present invention, the top ring is configured to be movable between a polishing position above the polishing table, and a substrate transfer position laterally of the polishing position, and the nozzle is provided retractably laterally of the top ring located at the substrate transfer position.

According to the present invention, the top ring and the connection-sheet cleaning nozzle can be prevented from interfering with each other, and thus the operation of the top ring is not hindered by the connection-sheet cleaning nozzle.

In a preferred aspect of the present invention, the nozzle comprises a nozzle which has a flattened portion, at a tip thereof, configured to be flattened and extending in a horizontal direction.

According to the present invention, the flattened portion extending in a horizontal direction is provided at the tip of the connection-sheet cleaning nozzle. In the case where the connection sheet is configured in a shape of bellows, the flattened portion at the tip of the connection-sheet cleaning nozzle is inserted into inner portions of folded and overlapped portions of the connection sheet, and thus the flow of the cleaning liquid can directly reach the connection sheet reliably. Further, the cleaning liquid which has been used for cleaning can be well drained. Furthermore, since the connection-sheet cleaning nozzle employs the straight jet nozzle, an adequate liquid pressure of the cleaning liquid ejected from the connection-sheet cleaning nozzle can be ensured, so that the flow of the cleaning liquid can reach a deep inner portion of the connection sheet reliably.

In a preferred aspect of the present invention, the nozzle has a flattened portion, at a tip thereof, configured to be flattened and extending in a horizontal direction; and the flattened portion has a wedge shape so that a thickness of the flattened portion is gradually thinner from one end side to the other end side.

According to the present invention, the flattened portion has a wedge shape so that the thickness of the wedge shape is increased toward the downstream direction in which the top ring is rotated, and thus the cleaning water which has been discharged from the nozzle and used for cleaning can be well drained.

According to another aspect of the present invention, there is provided a polishing apparatus for polishing a substrate, comprising: a polishing table having a polishing surface; a top ring configured to hold a substrate and press the substrate against the polishing surface, the top ring having a seal member configured to cover a gap formed between a top ring body and an inner circumferential surface of a retainer ring which is vertically movably provided at a peripheral portion of the top ring body; and a nozzle configured to eject a cleaning liquid in a vertical direction toward the gap, formed between the top ring body and the inner circumferential surface of the retainer ring, and to apply a flow of the cleaning liquid directly onto the seal member for cleaning the seal member.

According to the present invention, by ejecting the cleaning liquid in a vertical direction toward the gap, formed between the top ring body and the inner circumferential surface of the retainer ring, to apply the flow of the cleaning liquid directly onto the seal member, the seal member can be cleaned by the cleaning liquid efficiently even if the seal member is configured in a deep concave shape so as to reach a deep inner portion of the gap. Further, the connection sheet is kept wet by the cleaning liquid if needed, to prevent the contaminants such as a polishing liquid attached to the connection sheet from being dried.

In a preferred aspect of the present invention, the seal member is formed integrally with an elastic membrane which is provided at a lower surface of the top ring body to form at least one pressure chamber at a lower portion of the top ring body.

In a preferred aspect of the present invention, the top ring is configured to be movable between a polishing position above the polishing table, and a substrate transfer position laterally of the polishing position, and the nozzle is provided retractably below the top ring located at the substrate transfer position.

According to the present invention, the top ring and the seal-member cleaning nozzle are prevented from interfering with each other, and thus the operation of the top ring is not hindered by the seal-member cleaning nozzle.

In a preferred aspect of the present invention, the nozzle comprises a straight jet nozzle.

According to the present invention, an adequate liquid pressure of the cleaning liquid ejected from the seal-member cleaning nozzle can be ensured, so that the flow of the cleaning liquid can reach the deep inner portion of the seal member reliably.

According to the present invention, the extendable and contractable connection sheet, for covering the gap formed between the retainer ring guide fixed to the top ring body and the retainer ring guided by the retainer ring guide to move vertically, and the extendable and contractable seal member, for covering the gap formed between the top ring body and the retainer ring, can be cleaned by the cleaning liquid efficiently. Thus, one of the causes which generate scratches on the substrate can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an entire structure of a polishing apparatus according to the present invention;

FIG. 2 is a schematic plan view showing the polishing apparatus according to the present invention;

FIG. 3 is a cross-sectional view showing a top ring shown in FIG. 1;

FIG. 4 is a cross-sectional view showing the top ring shown in FIG. 1;

FIG. 5 is a cross-sectional view showing the top ring shown in FIG. 1;

FIG. 6 is a cross-sectional view showing the top ring shown in FIG. 1;

FIG. 7 is a cross-sectional view showing the top ring shown in FIG. 1;

FIG. 8 is an enlarged view of A part of a retainer ring shown in FIG. 5;

FIG. 9 is a view showing the configuration of a retainer ring guide and a ring member;

FIG. 10 is an enlarged view of B part of the retainer ring shown in FIG. 5;

FIG. 11 is a view as viewed from line X-X of FIG. 10;

FIG. 12 is a schematic perspective view showing a connection-sheet cleaning nozzle;

FIGS. 13A and 13B are views showing a modified embodiment of the connection-sheet cleaning nozzle. FIG. 13A is a perspective view showing the connection-sheet cleaning nozzle, and FIG. 13B is a view as viewed from an arrow C of FIG. 13A;

FIG. 14 is a plan view showing the connection-sheet cleaning nozzle provided laterally of the top ring located at a substrate transfer position;

FIG. 15 is a plan view showing a seal-member cleaning nozzle provided laterally of the top ring located at the substrate transfer position; and

FIG. 16 is a sectional elevational view showing the top ring located at the substrate transfer position, the connection-sheet cleaning nozzle and the seal-member cleaning nozzle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing apparatus according to embodiments of the present invention will be described below with reference to FIGS. 1 through 14.

FIG. 1 is a schematic view showing an entire structure of a polishing apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic plan view showing the polishing apparatus. As shown in FIG. 1, the polishing apparatus comprises a polishing table 100, and a top ring 1 for holding a substrate W such as a semiconductor wafer as an object to be polished and pressing the substrate against a polishing surface on the polishing table 100.

The polishing table 100 is coupled via a table shaft 100 a to a motor (not shown) disposed below the polishing table 100. Thus, the polishing table 100 is rotatable about the table shaft 100 a. A polishing pad 101 is attached to an upper surface of the polishing table 100. An upper surface 101 a of the polishing pad 101 constitutes a polishing surface to polish a semiconductor wafer W. A polishing liquid supply nozzle 102 is provided above the polishing table 100 to supply a polishing liquid (slurry) Q onto the polishing pad 101 on the polishing table 100.

The top ring 1 is connected to a lower end of a top ring shaft 111, which is vertically movable with respect to a top ring head 110 by a vertically moving mechanism 124. When the vertically moving mechanism 124 moves the top ring shaft 111 vertically, the top ring 1 is lifted and lowered as a whole for positioning with respect to the top ring head 110. A rotary joint 125 is mounted on the upper end of the top ring shaft 111.

The vertically moving mechanism 124 for vertically moving the top ring shaft 111 and the top ring 1 comprises a bridge 128 on which the top ring shaft 111 is rotatably supported by a bearing 126, a ball screw 132 mounted on the bridge 128, a support base 129 supported by support posts 130, and an AC servomotor 138 mounted on the support base 129. The support base 129, which supports the AC servomotor 138 thereon, is fixedly mounted on the top ring head 110 by the support posts 130.

The ball screw 132 comprises a screw shaft 132 a coupled to the AC servomotor 138 and a nut 132 b threaded over the screw shaft 132 a. The top ring shaft 111 is vertically movable in unison with the bridge 128 by the vertically moving mechanism 124. When the AC servomotor 138 is energized, the bridge 128 moves vertically via the ball screw 132, and the top ring shaft 111 and the top ring 1 move vertically.

The top ring shaft 111 is connected to a rotary sleeve 112 by a key (not shown). The rotary sleeve 112 has a timing pulley 113 fixedly disposed therearound. A top ring motor 114 having a drive shaft is fixedly mounted on the top ring head 110. The timing pulley 113 is operatively coupled to a timing pulley 116 mounted on the drive shaft of the top ring motor 114 by a timing belt 115. When the top ring motor 114 is energized, the timing pulley 116, the timing belt 115, and the timing pulley 113 are rotated to rotate the rotary sleeve 112 and the top ring shaft 111 in unison with each other, thus rotating the top ring 1.

The top ring head 110 is supported on a top ring head shaft 117 rotatably supported on a frame (not shown). With this arrangement, the top ring 1 connected to the top ring head 110 is moved in association with the rotation of the top ring head shaft 117, between a polishing position P immediately above the polishing table 100, and a substrate transfer position T laterally of the polishing table 100 and at which a pusher or the like is disposed. FIG. 2 shows a state in which the top ring 1 is located at the polishing position P, and the top ring 1 located at the substrate transfer position T is shown by an imaginary line.

In the polishing apparatus constructed as shown in FIG. 1 and FIG. 2, the top ring 1 is configured to hold the substrate W on its lower surface. The top ring head 110 is pivotable (swingable) about the top ring head shaft 117. Thus, the top ring 1, which holds the substrate W on its lower surface at the substrate transfer position T, is moved to the polishing position P immediately above the polishing table 100 by pivotal movement of the top ring head 110. Then, the top ring 1 is lowered to press the substrate W against the surface (polishing surface) 101 a of the polishing pad 101. At this time, while the top ring 1 and the polishing table 100 are respectively rotated, a polishing liquid is supplied onto the polishing pad 101 by the polishing liquid supply nozzle 102 provided above the polishing table 100. The substrate W is brought into sliding contact with the polishing surface 101 a of the polishing pad 101. Thus, a surface of the substrate W is polished.

When the polishing of the substrate W is completed, the top ring 1 is moved from the polishing position P immediately above the polishing table 100 to the substrate transfer position T laterally of the polishing table 100 by pivotal movement of the top ring head 110. The polished substrate W is transferred from the top ring 1 to the pusher or the like at the substrate transfer position T, and then transferred to the next process.

FIGS. 3 through 7 are cross-sectional views showing the top ring 1 along a plurality of radial directions of the top ring 1.

As shown in FIGS. 3 through 7, the top ring 1 basically comprises a top ring body 2 for pressing a substrate W against the polishing surface 101 a, and a retainer ring 3 for directly pressing the polishing surface 101 a. The top ring body 2 includes an upper member 300 in the form of a circular plate, an intermediate member 304 attached to a lower surface of the upper member 300, and a lower member 306 attached to a lower surface of the intermediate member 304. The retainer ring 3 is attached to a peripheral portion of the upper member 300. As shown in FIG. 4, the upper member 300 is connected to the top ring shaft 111 by bolts 308. Further, the intermediate member 304 is fixed to the upper member 300 by bolts 309, and the lower member 306 is fixed to the upper member 300 by bolts 310. The top ring body 2 comprising the upper member 300, the intermediate member 304, and the lower member 306 is made of resin such as engineering plastics (e.g., PEEK).

As shown in FIG. 3, an elastic membrane 314 is attached to a lower surface of the lower member 306. The elastic membrane 314 is brought into contact with a rear face of the substrate W. The elastic membrane 314 is held on the lower surface of the lower member 306 by an annular edge holder 316 disposed radially outward and annular ripple holders 318 and 319 disposed radially inward of the edge holder 316. The elastic membrane 314 is made of a highly strong and durable rubber material such as ethylene propylene rubber (EPDM), polyurethane rubber, silicone rubber, or the like.

The edge holder 316 is held by the ripple holder 318, and the ripple holder 318 is held on the lower surface of the lower member 306 by a plurality of stoppers 320. As shown in FIG. 4, the ripple holder 319 is held on the lower surface of the lower member 306 by a plurality of stoppers 322. The stoppers 320 and the stoppers 322 are arranged along a circumferential direction of the top ring 1 at equal intervals.

As shown in FIG. 3, a central chamber 360 is formed at a central portion of the elastic membrane 314. The ripple holder 319 has a passage 324 communicating with the central chamber 360. The lower member 306 has a passage 325 communicating with the passage 324. The passage 324 of the ripple holder 319 and the passage 325 of the lower member 306 are connected to a fluid supply source (not shown). Thus, a pressurized fluid is supplied through the passages 325 and 324 to the central chamber 360.

The ripple holder 318 has claws 318 b and 318 c for pressing a ripple 314 b and an edge 314 c of the elastic membrane 314 respectively against the lower surface of the lower member 306. The ripple holder 319 has a claw 319 a for pressing a ripple 314 a of the elastic membrane 314 against the lower surface of the lower member 306.

As shown in FIG. 5, an annular ripple chamber 361 is formed between the ripple 314 a and the ripple 314 b of the elastic membrane 314. A gap 314 f is formed between the ripple holder 318 and the ripple holder 319 of the elastic membrane 314. The lower member 306 has a passage 342 communicating with the gap 314 f. Further, as shown in FIG. 3, the intermediate member 304 has a passage 344 communicating with the passage 342 of the lower member 306. An annular groove 347 is formed at a connecting portion between the passage 342 of the lower member 306 and the passage 344 of the intermediate member 304. The passage 342 of the lower member 306 is connected via the annular groove 347 and the passage 344 of the intermediate member 304 to a fluid supply source (not shown). Thus, a pressurized fluid is supplied through these passages to the ripple chamber 361. Further, the passage 342 is selectively connected to a vacuum pump (not shown). When the vacuum pump is operated, a substrate is attracted to the lower surface of the elastic membrane 314 by suction, thereby chucking the substrate.

As shown in FIG. 6, the ripple holder 318 has a passage 326 communicating with an annular outer chamber 362 formed by the ripple 314 b and the edge 314 c of the elastic membrane 314. The lower member 306 has a passage 328 communicating with the passage 326 of the ripple holder 318 via a connector 327. The intermediate member 304 has a passage 329 communicating with the passage 328 of the lower member 306. The passage 326 of the ripple holder 318 is connected via the passage 328 of the lower member 306 and the passage 329 of the intermediate member 304 to a fluid supply source (not shown). Thus, a pressurized fluid is supplied through these passages to the outer chamber 362.

As shown in FIG. 7, the edge holder 316 has a claw for holding an edge 314 d of the elastic membrane 314 on the lower surface of the lower member 306. The edge holder 316 has a passage 334 communicating with an annular edge chamber 363 formed by the edges 314 c and 314 d of the elastic membrane 314. The lower member 306 has a passage 336 communicating with the passage 334 of the edge holder 316. The intermediate member 304 has a passage 338 communicating with the passage 336 of the lower member 306. The passage 334 of the edge holder 316 is connected via the passage 336 of the lower member 306 and the passage 338 of the intermediate member 304 to a fluid supply source (not shown). Thus, a pressurized fluid is supplied through these passages to the edge chamber 363.

In the top ring 1, pressing forces for pressing a substrate against the polishing pad 101 can be adjusted at local areas of the substrate by adjusting pressures of fluid to be supplied to the respective pressure chambers formed between the elastic membrane 314 and the lower member 306 (i.e., the central chamber 360, the ripple chamber 361, the outer chamber 362, and the edge chamber 363).

FIG. 8 is an enlarged view of A part of the retainer ring 3 shown in FIG. 5. The retainer ring 3 serves to hold a peripheral edge of a substrate. As shown in FIG. 8, the retainer ring 3 comprises a cylinder 400 having a cylindrical shape with a closed upper end, a holder 402 attached to an upper portion of the cylinder 400, an elastic membrane 404 held in the cylinder 400 by the holder 402, a piston 406 connected to a lower end of the elastic membrane 404, and a ring member 408 which is pressed downward by the piston 406.

The ring member 408 comprises an upper ring member 408 a coupled to the piston 406, and a lower ring member 408 b which is brought into contact with the polishing surface 101. The upper ring member 408 a and the lower ring member 408 b are coupled by a plurality of bolts 409. The upper ring member 408 a is made of a metal material such as SUS or a material such as ceramics, and the lower ring member 408 b is made of a resin material such as PEEK or PPS.

As shown in FIG. 8, the holder 402 has a passage 412 communicating with the retainer chamber 413 formed by the elastic membrane 404. The upper member 300 has a passage 414 communicating with the passage 412 of the holder 402. The passage 412 of the holder 402 is connected via the passage 414 of the upper member 300 to a fluid supply source (not shown). Thus, a pressurized fluid is supplied through these passages 414 and 412 to the retainer chamber 413. Accordingly, by adjusting a pressure of the fluid to be supplied to the retainer chamber 9, the elastic membrane 404 can be expanded and contracted so as to vertically move the piston 406. Thus, the ring member 408 of the retainer ring 3 can be pressed against the polishing pad 101 under a desired pressure.

In this example, the elastic membrane 404 employs a rolling diaphragm formed by an elastic membrane having bent portions. When an inner pressure in a chamber defined by the rolling diaphragm is changed, the bent portions of the rolling diaphragm are rolled so as to widen the chamber. The diaphragm is not brought into sliding contact with outside components and is hardly expanded and contracted when the chamber is widened. Accordingly, friction due to sliding contact can extremely be reduced, and a lifetime of the diaphragm can be prolonged. Further, pressing forces under which the retainer ring 3 presses the polishing pad 101 can accurately be adjusted.

With the above arrangement, only the ring member 408 of the retainer ring 3 can be lowered. Accordingly, a constant distance can be maintained between the lower member 306 and the polishing pad 101 even if the ring member 408 of the retainer ring 3 is worn out. Further, since the ring member 408, which is brought into contact with the polishing pad 101, and the cylinder 400 are connected by the deformable elastic membrane 404, no bending moment is produced by offset loads. Thus, surface pressures by the retainer ring 3 can be made uniform, and the retainer ring 3 becomes more likely to follow the polishing pad 101.

Further, as shown in FIG. 8, the retainer ring 3 has a ring-shaped retainer ring guide 410 for guiding vertical movement of the ring member 408. The ring-shaped retainer ring guide 410 comprises an outer peripheral portion 410 a located at an outer circumferential side of the ring member 408 so as to surround an entire circumference of an upper portion of the ring member 408, an inner peripheral portion 410 b located at an inner circumferential side of the ring member 408, and an intermediate portion 410 c configured to connect the outer peripheral portion 410 a and the inner peripheral portion 410 b. The inner peripheral portion 410 b of the retainer ring guide 410 is fixed to the lower member 306 of the top ring 1 by a plurality of bolts 411. The intermediate portion 410 c configured to connect the outer peripheral portion 410 a and the inner peripheral portion 410 b has a plurality of openings 410 h which are formed at equal intervals in a circumferential direction of the intermediate portion 410 c.

FIG. 9 shows the configuration of the retainer ring guide 410 and the ring member 408. As shown in FIG. 9, the intermediate portion 410 c is in the form of a ring as an entirely circumferentially continuous element, and has a plurality of circular arc openings 410 h formed at equal intervals in a circumferential direction of the intermediate portion 410 c. In FIG. 9, the circular arc opening 410 h is shown by dashed lines.

On the other hand, the upper ring 408 a of the ring member 408 comprises a lower ring portion 408 a 1 in the form of a ring as an entirely circumferentially continuous element, and a plurality of upper circular arc portions 408 a 2 projecting upwardly at equal intervals in a circumferential direction from the lower ring portion 408 a 1. Each of the upper circular arc portions 408 a 2 passes through the circular arc opening 410 h and is coupled to the piston 406 (see FIG. 8).

As shown in FIG. 9, a thin metal ring 430 made of SUS or the like is fitted over the lower ring member 408 b. A coating layer 430 c made of a resin material such as PEEK•PPS filled with a filler such as polytetrafluoroethylene (PTFE) or PTFE is formed on an outer circumferential surface of the metal ring 430. The resin material such as PTFE or PEEK•PPS comprises a low friction material having a low coefficient of friction, and has excellent sliding characteristics. The low friction material is defined as a material having a low coefficient of friction of 0.35 or less. It is desirable that the low friction material has a coefficient of friction of 0.25 or less.

On the other hand, the inner circumferential surface of the outer peripheral portion 410 a of the retainer ring guide 410 constitutes a guide surface 410 g which is brought into sliding contact with the coating layer 430 c. The guide surface 410 g has an improved surface roughness by mirror processing. The mirror processing is defined as a processing including polishing, lapping, and buffing.

As shown in FIG. 9, since the metal ring 430 made of SUS or the like is fitted over the lower ring member 408 b, the lower ring member 408 b has an improved rigidity. Thus, even if a temperature of the lower ring member 408 b increases due to the sliding contact between the lower ring member 408 b and the polishing surface 101 a, thermal deformation of the lower ring member 408 b can be suppressed. Therefore, a clearance between outer circumferential surfaces of the metal ring 430 and the lower ring member 408 b and an inner circumferential surface of the outer peripheral portion 410 a of the retainer ring guide 410 can be narrowed, and during polishing, abnormal noise or vibration generated at the time of collision between the retainer ring guide 410 and the ring member 408 caused by movement of the ring member 408 in the clearance can be suppressed. Further, since the coating layer 430 c formed on the outer circumferential surface of the metal ring 430 is composed of a low friction material, and the guide surface 410 g of the retainer ring guide 410 has an improved surface roughness by mirror processing, the sliding characteristics between the lower ring member 408 b and the retainer ring guide 410 can be improved. Thus, the following capability of the ring member 408 with respect to the polishing surface can be remarkably enhanced, and a desired surface pressure of the retainer ring can be applied to the polishing surface.

FIG. 10 is an enlarged view of B part of the retainer ring shown in FIG. 5, and FIG. 11 is a view as viewed from line X-X of FIG. 10. As shown in FIGS. 10 and 11, substantially oblong grooves 418 extending vertically are formed in the outer circumferential surface of the upper ring member 408 a of the ring member 408 of the retainer ring 3. A plurality of oblong grooves 418 are formed at equal intervals in the outer circumferential surface of the upper ring member 408 a. A plurality of driving pins 349 projecting radially inwardly are provided on the outer peripheral portion 410 a of the retainer ring guide 410. The driving pins 349 are configured to be engaged with the oblong grooves 418 of the ring member 408, respectively. The ring member 408 and the driving pin 349 are slidable vertically relative to each other in the oblong groove 418, and the rotation of the top ring body 2 is transmitted through the upper member 300 and the retainer ring guide 410 to the retainer ring 3 by the driving pins 349 to rotate the top ring body 2 and the retainer ring 3 integrally. A rubber cushion 350 is provided on the outer circumferential surface of the driving pin 349, and a collar 351 made of a low friction material such as PTFE or PEEK•PPS is provided on the outer side of the rubber cushion 350. Further, mirror processing is applied to the inner surface of the oblong groove 418 to improve surface roughness of the inner surface of the oblong groove 418 with which the collar 351 made of a low friction material is bought into contact.

As shown in FIGS. 3 through 10, a connection sheet 420 in a shape of bellows, which can be expanded and contracted in a vertical direction, is provided between an outer circumferential surface of the ring member 408 and a lower end of the retainer ring guide 410. The connection sheet 420 is disposed so as to fill a gap between the ring member 408 and the retainer ring guide 410. Thus, the connection sheet 420 serves to prevent a polishing liquid (slurry) from being introduced into the gap between the ring member 408 and the retainer ring guide 410. A band 421 comprising a belt-like flexible member is provided on an outer circumferential surface of the cylinder 400 and an outer circumferential surface of the retainer ring guide 410. The band 421 is disposed so as to cover a gap between the cylinder 400 and the retainer ring guide 410. Thus, the band 421 serves to prevent a polishing liquid (slurry) from being introduced into the gap between the cylinder 400 and the retainer ring guide 410.

The elastic membrane 314 includes a seal member 422 connecting the elastic membrane 314 to the retainer ring 3 at an edge (periphery) 314 d of the elastic membrane 314. The seal member 422 has an upwardly curved shape. The seal member 422 is disposed so as to fill a gap between the elastic membrane 314 and the ring member 408. The seal member 422 is made of a deformable material. The seal member 422 serves to prevent a polishing liquid from being introduced into the gap between the elastic membrane 314 and the ring member 408 while allowing the top ring body 2 and the retainer ring 3 to be moved relative to each other. In this example, the seal member 422 is formed integrally with the edge 314 d of the elastic membrane 314 and has a U-shaped cross-section.

If the connection sheet 420, the band 421 and the seal member 422 are not provided, a polishing liquid may be introduced into an interior of the top ring 1 so as to inhibit normal operation of the top ring body 2 and the retainer ring 3 of the top ring 1. In this example, the connection sheet 420, the band 421 and the seal member 422 prevent a polishing liquid from being introduced into the interior of the top ring 1. Accordingly, it is possible to operate the top ring 1 normally. The elastic membrane 404, the connection sheet 420, and the seal member 422 are made of a highly strong and durable rubber material such as ethylene propylene rubber (EPDM), polyurethane rubber, silicone rubber, or the like.

In the top ring 1 of this example, pressing forces to press a substrate against a polishing surface are controlled by pressures of fluid to be supplied to the central chamber 360, the ripple chamber 361, the outer chamber 362, and the edge chamber 363 formed by the elastic membrane 314. Accordingly, the lower member 306 should be located away upward from the polishing pad 101 during polishing. However, if the retainer ring 3 is worn out, a distance between the substrate and the lower member 306 is varied to change a deformation manner of the elastic membrane 314. Thus, surface pressure distribution with respect to the substrate is also varied. Such a variation of the surface pressure distribution causes unstable profiles of polished substrate. In this example, since the retainer ring 3 can vertically be moved independently of the lower member 306, a constant distance can be maintained between the substrate and the lower member 306 even if the ring member 408 of the retainer ring 3 is worn out. Accordingly, profiles of polished substrate can be stabilized.

In the illustrated example, the elastic membrane 314 is disposed so as to be brought into contact with substantially the entire surface of the substrate. However, the elastic membrane 314 may be brought into contact with at least a portion of a substrate. Further, the seal member 422 is formed integrally with the elastic membrane 314, however, the seal member 422 may be formed separately from the elastic membrane 314.

In this example, because the top ring 1 is configured such that the retainer ring 3 is vertically movably provided at the peripheral portion of the top ring body 2, the gaps are formed between the top ring body 2 and the retainer ring 3, and between the retainer ring 3 and the retainer ring guide 410. Therefore, in order to prevent a polishing liquid to be introduced into an interior of the top ring 1 through these gaps, the connection sheet 420, the band 421 and the seal member 422 are provided. Since the band 421 has a flat surface, the surface of the band 421 is cleaned easily by a cleaning water which is sprayed onto the top ring 1 to clean the top ring 1. However, the connection sheet 420 is formed in a shape of bellows or the like so as to expand and contract sufficiently, and the seal member 422 is formed in a deep concave shape so as to reach a deep inner portion of the gap formed between the elastic membrane 314, which covers the lower surface of the lower member 306 of the top ring body 2, and the inner circumferential surface of the ring member 408 of the retainer ring 3. Therefore, it is generally difficult to clean the entire surfaces of the bellows-like connection sheet 420 and the deep-concave-shaped seal member 422 by a cleaning water which is sprayed onto the top ring 1.

Accordingly, as shown in FIG. 2, a connection-sheet cleaning nozzle 500 is provided laterally of the top ring 1 located at the substrate transfer position T, for cleaning the connection sheet 420 by ejecting a cleaning water in a horizontal direction. Further, a seal-member cleaning nozzle 502 is provided laterally of the top ring 1 and also below the top ring 1 located at the substrate transfer position T, for cleaning the seal member 422 by ejecting a cleaning water in a vertical direction toward the gap formed between the elastic membrane 314, which covers the lower surface of the lower member 306 of the top ring body 2, and the inner circumferential surface of the ring member 408 of the retainer ring 3. The connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are attached to a support unit for supporting the top ring head shaft 117 in such a mariner that the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are vertically spaced one above the other.

FIG. 12 is a perspective view showing the connection-sheet cleaning nozzle 500. As shown in FIG. 12, the connection-sheet cleaning nozzle 500 is configured in an L-shape and has a nozzle unit 508 having an upwardly-opened cleaning water inlet 504 and a laterally-opened cleaning water outlet 506, and a link portion 510. The cleaning water inlet 504 and the cleaning water outlet 506 communicate with each other, and the cleaning water is ejected from the cleaning water outlet 506 in a horizontal direction toward the connection sheet 420. In this example, the connection-sheet cleaning nozzle 500 employs a nozzle for ejecting a cleaning water from the cleaning water outlet 506. A flattened portion 512 having a flattened shape and extending in a horizontal direction is formed at the tip of the nozzle unit 508, and the cleaning water outlet 506 is formed at the flattened portion 512. The flattened portion 512 has a vertical thickness which is set in the range of 2 to 3 mm. The flattened portion 512 has a central portion, having the cleaning water outlet 506, which is the most projecting part (the longest part), and both side portions which are gradually shorter from the central portion. Thus, the flattened portion 512 has a substantially semicircular planar shape. The length (L) of the most projecting part of the flattened portion 512 is set to 5 mm.

A shaft insert hole 514 for inserting an aftermentioned shaft 522, and a stopper portion 516 for limiting the movement (rotation) of the connection-sheet cleaning nozzle 500 by being brought into contact with an aftermentioned stopper 530 are provided at the base of the nozzle unit 508. A coupling pin insert hole 518 for inserting an aftermentioned coupling pin 528 is provided at the tip of the link portion 510.

FIGS. 13A and 13B are views showing a modified embodiment of the connection-sheet cleaning nozzle 500. FIG. 13A is a perspective view showing the connection-sheet cleaning nozzle 500, and FIG. 13B is a view as viewed from an arrow C of FIG. 13A. In the modified embodiment shown in FIGS. 13A and 13B, the flattened portion 512 has a wedge shape as viewed from the arrow C. As shown in FIG. 13B, the wedge shape has a right side end which is the thickest part of 2 mm to 3 mm, and is thinner from the right side end toward a left side. The wedge shape has a left side end which is sharpened. Other structure is the same as that of the connection-sheet cleaning nozzle 500 shown in FIG. 12.

As shown in FIG. 14, the connection-sheet cleaning nozzle 500 is provided laterally of the top ring 1 located at the substrate transfer position T so as to move (rotate) between a retracted position shown by solid lines, and a cleaning position shown by imaginary lines in a state in which the nozzle unit 508 is directed to the horizontal direction. At the retracted position, the nozzle unit 508 does not interfere with the movement (substrate transfer movement) of the top ring 1, and at the cleaning position, the cleaning water is ejected in a horizontal direction from the nozzle unit 508 toward the connection sheet 420.

Specifically, the connection-sheet cleaning nozzle 500 is supported by a fixing bracket 520 so as to be rotatable about the shaft 522, which is fixed to the fixing bracket 520 and inserted in the shaft insert hole 514, in a state in which the nozzle unit 508 is directed to the horizontal direction. The fixing bracket 520 is fixed to a support unit 118 configured to support the top ring head shaft 117 for swinging the top ring 1. Then, the tip of the link portion 510 is rotatably coupled to a tip of a cylinder rod 526 of a cylinder 524 by inserting the coupling pin 528 attached to the tip of the cylinder rod 526 of the cylinder 524 into the coupling pin insert hole 518. The base of the cylinder 524 is rotatably supported by the fixing bracket 520. Further, the stopper 530 comprising a bolt is mounted on the fixing bracket 520 to limit the excessive rotation of the connection-sheet cleaning nozzle 500 by being brought into contact with the stopper portion 516 of the link portion 510 when the connection-sheet cleaning nozzle 500 is located at the cleaning position.

With this configuration, when the cylinder rod 526 is retracted, the connection-sheet cleaning nozzle 500 is located at the retracted position at which the nozzle unit 508 does not project toward the top ring 1 located at the substrate transfer position T. The cylinder rod 526 is extended to allow the connection-sheet cleaning nozzle 500 to be rotated about the shaft 522, thereby swinging the nozzle unit 508 toward the top ring 1 located at the substrate transfer position T. Consequently, the connection-sheet cleaning nozzle 500 is located at the cleaning position.

Then, as shown in FIG. 16, when the connection-sheet cleaning nozzle 500 is moved (rotated) from the retracted position to the cleaning position, the flattened portion 512 of the nozzle unit 508 is inserted into the inner portions of the folded and overlapped portions of the bellows-like connection sheet 420. In this state, the cleaning water is ejected in a horizontal direction from the cleaning water outlet 506 of the nozzle unit 508, and hence a flow of the cleaning water reaches the connection sheet 420 directly, especially reaches the inner portions of the folded and overlapped portions of the connection sheet 420. Accordingly, the inner portions of the folded and overlapped portions of the connection sheet 420 can be cleaned efficiently, thereby reliably removing contaminants such as a polishing liquid which are liable to accumulate at the inner portions of the folded and overlapped portions.

In this manner, by ejecting the cleaning water in a horizontal direction toward the connection sheet 420 of the top ring 1 to apply the flow of the cleaning water directly onto the connection sheet 420, the connection sheet 420 can be cleaned by the cleaning water efficiently even if the connection sheet 420 is configured in a shape of bellows. Further, the connection sheet 420 is kept wet periodically by the cleaning water in a standby condition or the like if needed, to prevent the contaminants such as a polishing liquid attached to the connection sheet 420 from being dried. Thus, subsequent cleaning of the connection sheet 420 can be performed easily.

Especially, in the case where the flattened portion 512 is provided at the tip of the nozzle unit 508 of the connection-sheet cleaning nozzle 500 and the connection sheet 420 is configured in a shape of bellows, the flattened portion 512 of the nozzle unit 508 is inserted into the inner portions of the folded and overlapped portions of the bellows-like connection sheet 420. Therefore, the flow of the cleaning water can directly reach the connection sheet 420 reliably. When the connection-sheet cleaning nozzle 500 shown in FIGS. 13A and 13B is inserted into the inner portions of the folded and overlapped portions of the bellows-like connection sheet 420, the flattened portion 512 has a wedge shape so that the thickness of the wedge shape is increased toward the downstream direction in which the top ring 1 is rotated, and thus the cleaning water which has been discharged from the nozzle and used for cleaning can be well drained.

As shown in FIG. 15, the seal-member cleaning nozzle 502 is provided laterally of the top ring 1 and below the top ring 1 located at the substrate transfer position T so as to move (rotate) between a retracted position (shown by solid lines) where a nozzle unit 538 does not interfere with the movement of the top ring 1, and a cleaning position (shown by imaginary lines) where the nozzle unit 538 ejects the cleaning water in a vertical direction toward the seal member 422.

The seal-member cleaning nozzle 502 is configured to allow the nozzle unit 538 to be swingable by a cylinder and link mechanism in the same manner as the connection-sheet cleaning nozzle 500. Specifically, a fixing bracket 620 is fixed to the support unit 118 configured to support the top ring head shaft 117, and a base of a cylinder 624 is rotatably supported by the fixing bracket 620. An L-shaped link member 610 is coupled to a tip of a cylinder rod 626 of a cylinder 624. The link member 610 is configured to be swingable (rotatable) about a shaft 622 fixed to the fixing bracket 620. A plate-like support member 630 is fixed to the link member 610, and the nozzle unit 538 is supported by the support member 630. Thus, the seal-member cleaning nozzle 502 is configured such that when the cylinder rod 626 is retracted, the nozzle unit 538 is located at the retracted position (shown by solid lines), and when the cylinder rod 626 is extended, the L-shaped link member 610 is rotated about the shaft 622 to locate the nozzle unit 538 at the cleaning position (shown by imaginary lines).

As shown in FIG. 16, the nozzle unit 538 of the seal-member cleaning nozzle 502 has a horizontal portion 540 extending in a horizontal direction and a vertical portion 542 extending upward at a right angle from the horizontal portion 540, and is configured to eject a cleaning water vertically from a cleaning water outlet 544 at the tip of the vertical portion 542. The nozzle unit 538 of the seal-member cleaning nozzle 502 is provided laterally of the top ring 1 and also below the top ring 1 located at the substrate transfer position T so as to move between a retracted position shown by imaginary lines, and a cleaning position shown by solid lines. At the retracted position, the nozzle unit 538 does not interfere with the movement (substrate transfer movement) of the top ring 1, and at the cleaning position, the vertical portion 542 of the nozzle unit 538 is located at immediately below the gap between the elastic membrane 314, covering the lower surface of the lower member 306 of the top ring body 2, and the inner circumferential surface of the ring member 408 of the retainer ring 3. In this example, the seal-member cleaning nozzle 502 employs a straight jet nozzle for ejecting a cleaning water in a straight flow from the cleaning water outlet 544. The straight jet nozzle is configured to have a straight portion having a length of 5 mm or more and a cleaning water outlet provided at a tip of the straight portion, and to allow a discharge flow of a cleaning water ejected from the cleaning water outlet to go straight.

According to the seal-member cleaning nozzle 502, when the seal-member cleaning nozzle 502 is located at the cleaning position, the cleaning water is ejected in a vertical direction from the cleaning water outlet 544 toward the gap between the elastic membrane 314, covering the lower surface of the lower member 306 of the top ring body 2, and the inner circumferential surface of the ring member 408 of the retainer ring 3. Therefore, a flow of the cleaning water is applied onto the seal member 422 directly to clean the seal member 422. Thus, the seal member 422 can be cleaned by the cleaning water efficiently even if the seal member 422 is configured in a deep concave shape so as to reach a deep inner portion of the gap. Further, the seal member 422 is kept wet periodically by the cleaning water in a standby condition or the like if needed, to prevent the contaminants such as a polishing liquid attached to the seal member 422 from being dried. Thus, subsequent cleaning of the seal member 422 can be conducted easily.

Further, since the seal-member cleaning nozzle 502 employs the straight jet nozzle for allowing a flow of a cleaning water to move linearly, an adequate water pressure of the cleaning water ejected from the seal-member cleaning nozzle 502 can be ensured, so that the flow of the cleaning water can reach the deep inner portion of the seal member 422 reliably.

Next, specific dimensions of the respective parts will be described below. The width of the narrowest part of the gap between the retainer ring 3 and the elastic membrane 314 is about 1 mm, and the length from the lower surface of the elastic membrane 314 to the deepest part of the seal member 422 is about 20 mm. Thus, the length from the nozzle tip of the straight jet nozzle to the deepest part of the seal member 422 is in the range of 20 to 50 mm. The nozzle tip diameter is configured to be an orifice of 1 mm. The position of the nozzle is adjusted such that the center of the discharge flow of the nozzle is aligned with the center of the gap between the retainer ring 3 and the elastic membrane 314.

The seal member 422 is kept wet at all times by the discharge flow of the cleaning water discharged from the nozzle, thereby washing out the slurry or the like which enters into the gap. Thus, the seal-member cleaning nozzle 502 functions as a nozzle which is aimed at adhesion-prevention effect of the slurry.

Next, examples of the cleaning of the connection sheet 420 and the seal member 422 by the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 will be described below.

First, the top ring 1 which holds a polished substrate W is moved from the polishing position P to the substrate transfer position T, and the polished substrate is transferred from the top ring 1 to the pusher or the like. This transfer of the polished substrate W is detected. At this time, the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are located respectively at the retracted positions.

Next, the top ring 1 is rotated, and the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are moved from the retracted positions to the cleaning positions. Then, after the completion of movement of the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 to the cleaning positions is confirmed, ejecting of the cleaning water from the cleaning water outlets 506, 544 is started. Specifically, in the case of the connection-sheet cleaning nozzle 500, the flattened portion 512 at the tip of the nozzle unit 508 is located at the inner portions of the folded and overlapped portions of the bellows-like connection sheet 420, and the cleaning water is ejected in a horizontal direction from the cleaning water outlet 506. In the case of the seal-member cleaning nozzle 502, the cleaning water is ejected in a vertical direction from the cleaning water outlet 544 toward the gap between the elastic membrane 314, covering the lower surface of the lower member 306 of the top ring body 2, and the inner circumferential surface of the ring member 408 of the retainer ring 3. The top ring 1 may be started to rotate, after the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are moved from the retracted positions to the cleaning positions, and the completion of the respective movements to the cleaning positions is confirmed.

When the cleaning of the connection sheet 420 and the seal member 422 is completed, ejecting of the cleaning water from the cleaning water outlets 506, 544 of the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 is stopped, and then the rotation of the top ring 1 is stopped. Then, after the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 are moved to the retracted positions, the normal operation of the top ring 1 including the transfer of the substrate from the pusher, and the like is conducted.

In the case where the connection sheet 420 and the seal member 422 are made wet by the cleaning water ejected from the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 in a standby condition or the like, after the top ring 1 located at the predetermined substrate transfer position T is detected, the cleaning water is ejected from the cleaning water outlets 506, 544 of the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502, in substantially the same manner as the above.

A plurality of connection-sheet cleaning nozzles 500 and/or a plurality of seal-member cleaning nozzles 502 may be provided.

According to the polishing apparatus of the present invention, the connection sheet 420 and the seal member 422 are cleaned by the cleaning water ejected from the connection-sheet cleaning nozzle 500 and the seal-member cleaning nozzle 502 to reliably remove the contaminants such as a polishing liquid attached to the connection sheet 420 and the seal member 422. Thus, the surface of the object to be polished (substrate) such as a semiconductor wafer can be polished and planarized while preventing scratches caused by the contaminants such as a polishing liquid from occurring.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. 

What is claimed is:
 1. A polishing apparatus for polishing a substrate, comprising: a polishing table having a polishing surface; a top ring configured to hold a substrate and press the substrate against said polishing surface, said top ring having an extendable and contractable connection sheet configured to cover a gap between a retainer ring guide fixed to a top ring body and a retainer ring guided by said retainer ring guide to move vertically; and a nozzle configured to eject a cleaning liquid in a horizontal direction toward said connection sheet and apply a flow of the cleaning liquid directly onto said connection sheet for cleaning said connection sheet.
 2. A polishing apparatus according to claim 1, wherein said top ring is configured to be movable between a polishing position above said polishing table, and a substrate transfer position laterally of said polishing position, and said nozzle is provided retractably laterally of said top ring located at said substrate transfer position.
 3. A polishing apparatus according to claim 1, wherein said nozzle comprises a nozzle which has a flattened portion, at a tip thereof, configured to be flattened and extending in a horizontal direction.
 4. A polishing apparatus according to claim 1, wherein said nozzle has a flattened portion, at a tip thereof, configured to be flattened and extending in a horizontal direction; and said flattened portion has a wedge shape so that a thickness of said flattened portion is gradually thinner from one end side to the other end side.
 5. A polishing apparatus for polishing a substrate, comprising: a polishing table having a polishing surface; a top ring configured to hold a substrate and press the substrate against said polishing surface, said top ring having a seal member configured to cover a gap formed between a top ring body and an inner circumferential surface of a retainer ring which is vertically movably provided at a peripheral portion of said top ring body; and a nozzle configured to eject a cleaning liquid in a vertical direction toward said gap, formed between said top ring body and said inner circumferential surface of said retainer ring, and to apply a flow of the cleaning liquid directly onto said seal member for cleaning said seal member.
 6. A polishing apparatus according to claim 5, wherein said seal member is formed integrally with an elastic membrane which is provided at a lower surface of said top ring body to form at least one pressure chamber at a lower portion of said top ring body.
 7. A polishing apparatus according to claim 5, wherein said top ring is configured to be movable between a polishing position above said polishing table, and a substrate transfer position laterally of said polishing position, and said nozzle is provided retractably below said top ring located at said substrate transfer position.
 8. A polishing apparatus according to claim 5, wherein said nozzle comprises a straight jet nozzle. 